High temperature resistant salt water base drilling fluid suitable for long horizontal section well long invasion and preparation method thereof

Abstract

The application provides a high-temperature resistant brine-based drilling fluid suitable for long-time invasion in long horizontal section and a preparation method thereof, the drilling fluid comprises the following raw materials in parts by weight: bentonite 1-2 parts, attapulgite 1-3 parts, adhesion blocking agent 4-6 parts, water-soluble viscosity regulator 1-3 parts, polymer efficiency improver 1-5 parts, sodium formate 15-25 parts, sodium carbonate 0.2-0.8 parts, weighting agent 5-15 parts, the water-soluble viscosity regulator is obtained by mixing cotton, isopropyl alcohol and sodium hydroxide to obtain an intermediate alkali solution and then polymerizing chloroacetic acid and hydrochloric acid, and the polymer efficiency improver is obtained by solution polymerization of sodium hydroxide, humic acid, sodium pyrosulfite, formaldehyde, phenolic resin and hydrolyzed polyacrylonitrile. The components in the drilling fluid of the application have a synergistic effect, so that the drilling fluid system can effectively block the invasion of the drilling fluid under the conditions of long time, long horizontal section, high salt and high temperature and high pressure, the well wall is kept stable, and the well wall collapse and pipe sticking are prevented.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, specifically to a high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections and its preparation method. Background Technology

[0002] To more efficiently extract conventional energy sources such as oil and gas, as well as unconventional energy sources such as shale gas, coalbed methane, and natural gas hydrates, horizontal well drilling is often used in reservoir drilling. Scientific drilling and coring processes also face the challenges of drilling long horizontal sections. Compared to vertical wells, maintaining wellbore stability is more difficult in horizontal wells, and conventional drilling fluid systems are insufficient to maintain stability in long horizontal sections. With advancements in drilling technology, the length of long horizontal well sections is gradually increasing, leading to wellbore instability due to prolonged immersion and intrusion of drilling fluid. Furthermore, as drilling depth increases, formation temperatures rise, further complicating the stabilization of long horizontal well sections.

[0003] Chinese patent document CN110846003B discloses a weak magnetic targeted lubricant and a water-based drilling fluid containing the lubricant. This drilling fluid system can be applied to long horizontal drilling sections, but it only considers the lubrication efficiency of the horizontal well length and does not consider the influence of other drilling fluid performance parameters. Chinese patent document CN113980662A discloses an oil-based drilling fluid system for long horizontal wells with extended reach in shale gas operations. This drilling fluid system is suitable for long horizontal wells with extended reach in shale gas operations, but as an oil-based system, it can pollute the formation or groundwater, failing to meet environmental protection requirements. Chinese patent document CN111320972B discloses an amide-amino chitosan, its preparation method, and a drilling fluid. This drilling fluid system is suitable for long horizontal well drilling in shale oil and gas operations. However, its drilling fluid system uses amide-amino chitosan, which differs from this invention and does not consider the problem of long-term drilling fluid intrusion.

[0004] In the field of drilling fluid technology for long-term immersion in long horizontal sections, there is an urgent need to develop a high-temperature saline-based drilling fluid suitable for long-term immersion in long horizontal sections of wells, so as to provide technical support for more efficient drilling and energy resource extraction. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides a high-temperature resistant salt water-based drilling fluid suitable for long-term invasion in long horizontal wells and its preparation method. It can maintain wellbore stability during drilling of long horizontal wells, achieving high temperature resistance, high inhibition and environmental friendliness, and meeting the needs of long-term formation invasion drilling in long horizontal wells.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] In a first aspect, the present invention provides a high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, comprising the following raw materials in parts by weight: 1-2 parts bentonite, 1-3 parts attapulgite, 4-6 parts adhesive sealing agent, 1-3 parts water-soluble viscosity modifier, 1-5 parts polymer enhancer, 15-25 parts sodium formate, 0.2-0.8 parts sodium carbonate, and 5-15 parts weighting agent; the water-soluble viscosity modifier is prepared by the following method: cotton and isopropanol are mixed evenly, and sodium hydroxide is added to carry out an alkalization reaction to obtain an intermediate alkalization solution; the intermediate alkalization solution and chloroacetic acid are added to a reaction vessel, heated to the reaction temperature, and hydrochloric acid is added dropwise to react; after the reaction is completed, the solvent is removed, and the product is dried to obtain the water-soluble viscosity modifier; the polymer enhancer is prepared by the following method:

[0008] 1) Dissolve sodium hydroxide in water, add humic acid, then add sodium metabisulfite and formaldehyde, heat to a fixed temperature and react for a certain time to obtain sulfonated intermediate product I;

[0009] 2) Phenolic resin, sulfonated intermediate product I and hydrolyzed polyacrylonitrile are added to a reaction vessel and reacted. The product is dried and pulverized to obtain the polymer enhancer.

[0010] According to the above scheme, the solvent is removed by filtration during the preparation of the water-soluble viscosity modifier, and the product is crushed and dried. Preferably, the drying temperature is 90-100℃.

[0011] According to the above scheme, the mass ratio of cotton, isopropanol and sodium hydroxide is 1:(0.2-0.25):(0.7-0.77), and the mass ratio of the intermediate alkalization solution, chloroacetic acid and hydrochloric acid is 1:(1.4-1.5):(2-2.1) based on 36% hydrochloric acid.

[0012] According to the above scheme, the sodium hydroxide is added at a temperature of 25–35°C, and the alkalization reaction takes 60–70 minutes.

[0013] According to the above scheme, the reaction temperature of the intermediate alkalization solution, chloroacetic acid and hydrochloric acid is 65-75℃, and the reaction time is 80-90 min.

[0014] According to the above scheme, in the preparation process of the polymer enhancer, the mass ratio of sodium hydroxide to water is 1:3.8-4.3, the mass ratio of humic acid to water is 1:2-2.5, the mass ratio of sodium metabisulfite to water is 1:5-5.5, the mass ratio of formaldehyde to water is 1:9.5-10.2, and the mass ratio of phenolic resin, sulfonated intermediate product I and hydrolyzed polyacrylonitrile is 1:(1.6-2.2):(0.8-1.3).

[0015] According to the above scheme, the reaction temperature in step 1) is 90-100℃ and the reaction time is 3-4h, and the reaction temperature in step 2) is 93-97℃ and the reaction time is 3-4h.

[0016] According to the above scheme, the drying temperature in step 2) is 90-100℃.

[0017] According to the above scheme, the adhesive sealing agent is nano-silica, and the weighting agent is barite.

[0018] According to the above scheme, the particle size of the nano-silica is 20-100 nm.

[0019] Secondly, the present invention provides a method for preparing the above-mentioned high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, comprising the following steps: adding water to a high-speed stirring cup, adding bentonite and attapulgite under medium-speed stirring, stirring at medium speed for 16-18 hours, adding sodium carbonate, stirring at high speed for 15-20 minutes, adding an adhesion and plugging agent, stirring at high speed for 20-30 minutes, adding a water-soluble viscosity modifier, stirring at high speed for 20-30 minutes, adding a polymer performance enhancer, stirring at high speed for 15-20 minutes, adding sodium formate, stirring at high speed for 20-30 minutes, adding a weighting agent, and stirring at high speed for 20-30 minutes, thereby obtaining the high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, wherein the rotation speed of the medium-speed stirring is 1000-2000 r / min, and the rotation speed of the high-speed stirring is 6000-10000 r / min.

[0020] The principle of this invention is as follows: The drilling fluid system of this invention contains core treatment materials such as viscous plugging agent, water-soluble viscosity modifier, and polymer efficiency enhancer. Bentonite and attapulgite, as clay mineral particles, provide a specific carrier for the drilling fluid treatment agents to exert their effects. The adhesive plugging agent can play a good role in adhesion and filtration reduction, which can improve the wettability of the rock surface and adsorb onto the rock surface to reduce the intrusion of drilling fluid. In particular, the nano-silica particles, as inert materials, are smaller than the pore throats of sandstone and shale, and can enter various rock pores very well. Water-soluble viscosity modifiers are environmentally friendly and heat-resistant, and can adjust the rheological properties of drilling fluids. They can adsorb onto clay mineral particles and hydrophilic nano-silica particles, entering the interior of rock pores and increasing the inhibition performance of the drilling fluid. Furthermore, water-soluble viscosity modifiers can form a network structure in the drilling fluid, increasing its viscosity and shear force, thereby carrying rock cuttings and maintaining wellbore stability. Polymer enhancers can prevent filtrate from further entering rock pores and interact with the formation, maintaining long-term wellbore stability in long horizontal sections and reducing drilling risks. The fibrous material of the water-soluble viscosity modifier can adsorb onto the lipid material in the polymer enhancer, enhancing the polymer enhancer's inhibition and heat resistance. Sodium formate provides a high concentration of formate ions, maintaining the inhibition performance of the drilling fluid system.

[0021] The beneficial effects of this invention are: the synergistic effect of the components in the drilling fluid of this invention enables the drilling fluid system to effectively resist the intrusion of drilling fluid under long-term, long-horizontal-section, high-salt, high-temperature and high-pressure conditions, maintain wellbore stability, prevent wellbore collapse and stuck pipe, and facilitate maintenance; it can meet the needs of horizontal well drilling into intrusive formations under conditions of 240 hours, 200℃, and a salt concentration of 16-20wt%, and its environmental friendliness is EC. 50 The concentration is 30,000–50,000 mg / L, and the preparation method is simple, showing broad application prospects. Attached Figure Description

[0022] Figure 1 This is a SEM image of the water-soluble viscosity modifier prepared in Example 1 of the present invention;

[0023] Figure 2 This is an elemental analysis diagram of the water-soluble viscosity modifier prepared in Example 1 of the present invention. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] It should be noted that, in the description of the embodiments of this application, the term "some specific embodiments" means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same implementation or instance. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0026] To address the shortcomings of long-term invasive drilling in long horizontal sections, this invention employs core processing materials such as bentonite, attapulgite, viscous plugging agent, water-soluble viscosity modifier, and polymer performance enhancer. By adding sodium formate, sodium carbonate, and weighting agents, a high-temperature resistant brine-based drilling fluid suitable for long-term invasive drilling in long horizontal sections is formed. This fluid can maintain wellbore stability during drilling in long horizontal sections, achieving high temperature resistance, high inhibition, and environmental friendliness, thus meeting the needs of drilling long-term invasive formations in long horizontal sections.

[0027] The high-temperature saline-based drilling fluid of the present invention, suitable for long-term invasion in long horizontal well sections, comprises the following raw materials in parts by weight: 1-2 parts bentonite, 1-3 parts attapulgite, 4-6 parts adhesive sealing agent, 1-3 parts water-soluble viscosity modifier, 1-5 parts polymer enhancer, 15-25 parts sodium formate, 0.2-0.8 parts sodium carbonate, and 5-15 parts weighting agent; the water-soluble viscosity modifier is prepared by the following method: cotton and isopropanol are mixed evenly, and sodium hydroxide is added to carry out an alkalization reaction to obtain an intermediate alkalization solution. The intermediate alkalization solution and chloroacetic acid are added to a reaction vessel, heated to the reaction temperature, and hydrochloric acid is added dropwise to react. After the reaction is completed, the solvent is removed, and the product is dried to obtain the water-soluble viscosity modifier; the polymer enhancer is prepared by the following method:

[0028] 1) Dissolve sodium hydroxide in water, add humic acid, then add sodium metabisulfite and formaldehyde, heat to a fixed temperature and react for a certain time to obtain sulfonated intermediate product I;

[0029] 2) Phenolic resin, sulfonated intermediate product I and hydrolyzed polyacrylonitrile are added to a reaction vessel and reacted. The product is dried and pulverized to obtain the polymer enhancer.

[0030] In some specific embodiments, the mass ratio of cotton, isopropanol and sodium hydroxide in the preparation of the water-soluble viscosity modifier is 1:(0.2-0.25):(0.7-0.77), and the mass ratio of the intermediate alkalization solution, chloroacetic acid and hydrochloric acid is 1:(1.4-1.5):(2-2.1) based on 36% hydrochloric acid.

[0031] In some specific embodiments, the sodium hydroxide is added at a temperature of 25–35°C, and the alkalization reaction takes 60–70 minutes.

[0032] In some specific embodiments, the reaction temperature of the intermediate alkalization solution, chloroacetic acid and hydrochloric acid is 65-75°C, and the reaction time is 80-90 min.

[0033] In some specific embodiments, during the preparation of the polymer enhancer, the mass ratio of sodium hydroxide to water is 1:3.8-4.3, the mass ratio of humic acid to water is 1:2-2.5, the mass ratio of sodium metabisulfite to water is 1:5-5.5, the mass ratio of formaldehyde to water is 1:9.5-10.2, and the mass ratio of phenolic resin, sulfonated intermediate product I, and hydrolyzed polyacrylonitrile is 1:(1.6-2.2):(0.8-1.3).

[0034] Preferably, the reaction temperature in step 1) is 90-100℃ and the reaction time is 3-4h, and the reaction temperature in step 2) is 93-97℃ and the reaction time is 3-4h.

[0035] Preferably, the drying temperature in step 2) is 90–100°C.

[0036] In some specific embodiments, the adhesive sealing agent is nano-silica, and the weighting agent is barite.

[0037] In some specific embodiments, the particle size of the nano-silica is 20–100 nm.

[0038] This invention also provides a method for preparing the above-mentioned high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, comprising the following steps: adding water to a high-speed stirring cup, adding bentonite and attapulgite under medium-speed stirring, stirring at medium speed for 16-18 hours, adding sodium carbonate, stirring at high speed for 15-20 minutes, adding an adhesion and plugging agent, stirring at high speed for 20-30 minutes, adding a water-soluble viscosity modifier, stirring at high speed for 20-30 minutes, adding a polymer performance enhancer, stirring at high speed for 15-20 minutes, adding sodium formate, stirring at high speed for 20-30 minutes, adding a weighting agent, and stirring at high speed for 20-30 minutes, thereby obtaining the high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, wherein the medium-speed stirring speed is 1000-2000 r / min and the high-speed stirring speed is 6000-10000 r / min.

[0039] Based on the above embodiments, the present invention provides the following specific examples to further illustrate the invention. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following examples, unless otherwise specified, are generally performed according to the manufacturer's recommended conditions. Unless otherwise stated, percentages and parts are calculated by mass. The experimental methods described in the examples are conventional methods unless otherwise specified; the additives and materials used are commercially available unless otherwise specified.

[0040] Example

[0041] This embodiment provides a high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, comprising the following components by weight: 100 parts water, 2 parts bentonite, 2 parts attapulgite, 4 parts adhesive plugging agent, 2 parts water-soluble viscosity modifier, 3 parts polymer enhancer, 20 parts sodium formate, 0.4 parts sodium carbonate, and 10 parts weighting agent.

[0042] The adhesive sealant is nano-silica, and the weighting agent is barite.

[0043] The preparation method of the polymer performance enhancer is as follows:

[0044] (1) Dissolve sodium hydroxide in water, with a mass ratio of sodium hydroxide to water of 1:4. Slowly add humic acid, with a mass ratio of humic acid to water of 1:2. Then add sodium metabisulfite and formaldehyde, with a mass ratio of sodium metabisulfite to water of 1:5 and a mass ratio of formaldehyde to water of 1:10. Heat to 100℃ and react for 3 hours to obtain sulfonated intermediate product 1.

[0045] (2) Phenolic resin, sulfonated intermediate product 1 and hydrolyzed polyacrylonitrile are added to a reaction vessel and reacted. The mass ratio of phenolic resin, sulfonated intermediate product 1 and hydrolyzed polyacrylonitrile is 1:2:1. The polymer enhancer is obtained by drying and pulverizing at 110°C.

[0046] The preparation method of water-soluble viscosity modifier is as follows:

[0047] (1) Cotton and isopropanol were mixed and stirred. The mass ratio of cotton, isopropanol and sodium hydroxide was 1:0.24:0.73. After mixing evenly, sodium hydroxide was added to obtain an intermediate alkalization solution. Sodium hydroxide was added at 30°C and the alkalization reaction time was 60 minutes.

[0048] (2) Add the intermediate body alkalization solution and chloroacetic acid to the reaction vessel, add hydrochloric acid dropwise, and carry out the reaction. The mass ratio of intermediate body alkalization solution, chloroacetic acid and hydrochloric acid is 1:1.46:2.01. Heat to 70°C and react for 90 minutes. After the reaction is completed, cool to room temperature, filter to remove the solvent, crush the product and dry at 90°C to obtain a water-soluble viscosity modifier.

[0049] The prepared water-soluble viscosity modifier was observed under a scanning electron microscope, and the results are as follows: Figure 1 As shown, the prepared water-soluble viscosity modifiers have various shapes and sizes on the micrometer scale.

[0050] Figure 2 The elemental analysis diagram of the prepared water-soluble viscosity modifier shows that its main elements are carbon, oxygen, sodium, and chlorine.

[0051] The preparation method of the high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections in this embodiment is as follows:

[0052] Water was placed in the agitator cup, and bentonite and attapulgite were added while stirring for 18 hours. Sodium carbonate was added and stirred for 15 minutes. Adhesive and plugging agent was added and stirred for 30 minutes. Water-soluble viscosity modifier was added and stirred for 30 minutes. Polymer performance enhancer was added and stirred for 20 minutes. Sodium formate was added and stirred for 30 minutes. Weighting agent was added and stirred for 20 minutes to obtain high-temperature salt water-based drilling fluid 1 for long-term invasion of long horizontal well sections.

[0053] Example 2

[0054] This embodiment provides a high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, comprising the following components by weight:

[0055] 100 parts water, 1 part bentonite, 3 parts attapulgite, 6 parts adhesive sealant, 2 parts water-soluble viscosity modifier, 4 parts polymer enhancer, 18 parts sodium formate, 0.3 parts sodium carbonate, and 15 parts weighting agent.

[0056] The viscous plugging agent is nano-silica, the weighting agent is barite, and the preparation methods of the water-soluble viscosity modifier and polymer performance enhancer are the same as in Example 1. The preparation method of the above-mentioned high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal wells is also the same as in Example 1, thus obtaining the high-temperature saline-based drilling fluid 2 suitable for long-term invasion in long horizontal wells.

[0057] Example 3

[0058] This embodiment provides a high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, comprising the following components by weight:

[0059] 100 parts water, 2 parts bentonite, 3 parts attapulgite, 5 parts adhesive sealant, 3 parts water-soluble viscosity modifier, 3 parts polymer enhancer, 16 parts sodium formate, 0.4 parts sodium carbonate, and 10 parts weighting agent.

[0060] The viscous plugging agent is nano-silica, the weighting agent is barite, and the preparation methods of the water-soluble viscosity modifier and polymer performance enhancer are the same as in Example 1. The preparation method of the above-mentioned high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal wells is also the same as in Example 1, thus obtaining the high-temperature saline-based drilling fluid 3 suitable for long-term invasion in long horizontal wells.

[0061] Comparative Example 1

[0062] This comparative example provides a drilling fluid for long-term penetration in a long horizontal section well, comprising the following components in parts by weight:

[0063] 100 parts water, 1 part bentonite, 3 parts attapulgite, 6 parts adhesive sealant, 4 parts polymer enhancer, 18 parts sodium formate, 0.3 parts sodium carbonate, and 15 parts weighting agent.

[0064] The viscous plugging agent is nano-silica, the weighting agent is barite, and the preparation method of the polymer performance enhancer is the same as in Example 1. The preparation method of the drilling fluid for long-term invasion in the long horizontal section well in this comparative example is the same as in Example 1, and drilling fluid C1 for long-term invasion in the long horizontal section well is obtained.

[0065] Comparative Example 2

[0066] This comparative example provides a drilling fluid for long-term penetration in a long horizontal section well, comprising the following components in parts by weight:

[0067] 100 parts water, 2 parts bentonite, 2 parts attapulgite, 4 parts adhesive sealant, 2 parts water-soluble viscosity modifier, 20 parts sodium formate, 0.4 parts sodium carbonate, and 10 parts weighting agent.

[0068] The viscous plugging agent is nano-silica, the weighting agent is barite, and the preparation method of the water-soluble viscosity modifier is the same as in Example 1. The preparation method of the drilling fluid for long-term invasion in the long horizontal section well in this comparative example is the same as in Example 1, and drilling fluid C2 for long-term invasion in the long horizontal section well is obtained.

[0069] Comparative Example 3

[0070] This comparative example provides a drilling fluid for long-term penetration in a long horizontal section well, comprising the following components in parts by weight:

[0071] 100 parts water, 2 parts bentonite, 3 parts attapulgite, 5 parts adhesive sealant, 16 parts sodium formate, 0.4 parts sodium carbonate, and 10 parts weighting agent.

[0072] The viscous plugging agent is nano-silica, the weighting agent is barite, and the drilling fluid for long-term invasion in long horizontal wells is prepared as described in Example 1, thus obtaining drilling fluid C3 for long-term invasion in long horizontal wells.

[0073] Comparative Example 4

[0074] This comparative example provides a drilling fluid for long-term penetration in a long horizontal section well, comprising the following components in parts by weight:

[0075] 100 parts water, 4 parts adhesive sealant, 2 parts water-soluble viscosity modifier, 3 parts polymer enhancer, 20 parts sodium formate, 0.4 parts sodium carbonate, and 10 parts weighting agent.

[0076] The viscous plugging agent is nano-silica, the weighting agent is barite, and the preparation methods of the water-soluble viscosity modifier and polymer efficiency enhancer are the same as in Example 1. The preparation method of the drilling fluid for long-term invasion in long horizontal wells is as described in Example 1, and drilling fluid C4 for long-term invasion in long horizontal wells is obtained.

[0077] Comparative Example 5

[0078] This comparative example provides a drilling fluid for long-term penetration in long horizontal wells. Unlike Example 3, the polymer enhancer is replaced with sulfonated lignite resin to obtain drilling fluid C5 for long-term penetration in long horizontal wells.

[0079] Comparative Example 6

[0080] This comparative example provides a drilling fluid for long-term penetration in a long horizontal section well, comprising the following components in parts by weight:

[0081] 100 parts water, 2 parts bentonite, 3 parts attapulgite, 5 parts adhesive sealant, 3 parts water-soluble viscosity modifier, 3 parts polymer enhancer, 16 parts sodium formate, and 0.4 parts sodium carbonate.

[0082] The viscous plugging agent is nano-silica, and the preparation methods of the water-soluble viscosity modifier and polymer efficiency enhancer are the same as in Example 1. The preparation method of the drilling fluid for long-term invasion in long horizontal wells is the same as in Example 1, and drilling fluid C6 for long-term invasion in long horizontal wells is obtained.

[0083] Test case

[0084] The drilling fluids prepared in the examples and comparative examples were tested for their performance at 200°C, and the results are shown in Table 1.

[0085] Table 1 Basic Properties of Drilling Fluids

[0086]

[0087] Experimental Example 2

[0088] The drilling fluids prepared in the examples and comparative examples were tested for their inhibition and environmental performance over 240 hours, and the results are shown in Table 2.

[0089] Table 2 Inhibition performance and environmental performance of drilling fluids

[0090]

[0091]

[0092] As can be seen from the data in Tables 1 and 2, drilling fluids 1-3 in Examples 1-3 exhibited good performance in high-temperature experiments, inhibition performance, and environmental performance. They were able to maintain wellbore stability during drilling of long horizontal sections, achieving high temperature resistance, high inhibition, and environmental friendliness, thus meeting the needs of long-term formation penetration drilling in long horizontal sections. Comparative drilling fluid C1 lacks a water-soluble viscosity modifier, thus failing to provide viscosity and shear strength, resulting in decreased inhibition performance. Comparative drilling fluid C2 lacks a polymer enhancer, leading to poor shear strength and viscosity effects. Comparative drilling fluid C3 lacks both water-soluble viscosity modifier and polymer enhancer, resulting in almost no viscosity and shear strength, significantly reducing inhibition performance and failing to meet the requirements for long-term, horizontal drilling into formations. Comparative drilling fluid C3 also lacks bentonite and attapulgite, rendering it unable to effectively enhance viscosity and shear strength. Comparative drilling fluid C5, which replaces the polymer enhancer with sulfonated lignite resin, has an environmental performance rating below 10,000, failing to meet environmental and emission standards. Comparative drilling fluid C6 lacks a weighting agent, resulting in insufficient drilling fluid density to effectively support formation pressure.

[0093] In summary, the high-temperature resistant salt water-based drilling fluid of the present invention, suitable for long-term intrusion drilling in long horizontal sections of wells, can maintain wellbore stability during drilling in long horizontal sections, achieving high temperature resistance, high inhibition, and environmental friendliness, thus meeting the needs of drilling long-term intrusion formations in long horizontal sections of wells.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, characterized in that, The raw materials include the following parts by weight: 1-2 parts bentonite, 1-3 parts attapulgite, 4-6 parts adhesive sealant, 1-3 parts water-soluble viscosity modifier, 1-5 parts polymer enhancer, 15-25 parts sodium formate, 0.2-0.8 parts sodium carbonate, and 5-15 parts weighting agent. The adhesive sealing agent is nano-silica; The water-soluble viscosity modifier is prepared by the following method: cotton and isopropanol are mixed evenly, and sodium hydroxide is added to carry out an alkalization reaction to obtain an intermediate alkalization solution. The intermediate alkalization solution and chloroacetic acid are added to a reaction vessel, heated to the reaction temperature, and hydrochloric acid is added dropwise to react. After the reaction is completed, the solvent is removed, and the product is dried to obtain the water-soluble viscosity modifier; wherein, the mass ratio of cotton, isopropanol and sodium hydroxide is 1:0.24:0.73, and the mass ratio of the intermediate alkalization solution, chloroacetic acid and hydrochloric acid is 1:1.46:2.

01. The polymer performance enhancer is prepared by the following method: 1) Dissolve sodium hydroxide in water, add humic acid, then add sodium metabisulfite and formaldehyde, heat to a fixed temperature and react for a certain time to obtain sulfonated intermediate product I; 2) Phenolic resin, sulfonated intermediate product I and hydrolyzed polyacrylonitrile are added to a reaction vessel and reacted. The product is dried and pulverized to obtain the polymer enhancer. In the preparation method of the polymer enhancer, the mass ratio of sodium hydroxide to water is 1:4, the mass ratio of humic acid to water is 1:2, the mass ratio of sodium metabisulfite to water is 1:5, the mass ratio of formaldehyde to water is 1:10, and the mass ratio of phenolic resin, sulfonated intermediate product I, and hydrolyzed polyacrylonitrile is 1:2:

1.

2. The high-temperature saline-based drilling fluid resistant to long-term invasion in long horizontal well sections according to claim 1, characterized in that, Sodium hydroxide is added at a temperature of 25-35℃, and the alkalization reaction takes 60-70 minutes.

3. The high-temperature saline-based drilling fluid resistant to long-term invasion in long horizontal well sections according to claim 1, characterized in that, The reaction temperature of the intermediate alkalization solution, chloroacetic acid and hydrochloric acid is 65~75℃, and the reaction time is 80~90min.

4. The high-temperature saline-based drilling fluid resistant to long-term invasion in long horizontal well sections according to claim 1, characterized in that, In step 1), the reaction temperature is 90~100℃ and the reaction time is 3~4h. In step 2), the reaction temperature is 93~97℃ and the reaction time is 3~4h.

5. The high-temperature saline-based drilling fluid resistant to long-term invasion in long horizontal well sections according to any one of claims 1 to 4, characterized in that, The weighting agent is barite.

6. The method for preparing a high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections, as described in any one of claims 1 to 5, is characterized in that... The process includes the following steps: adding water to a high-speed stirring cup, adding bentonite and attapulgite under medium-speed stirring for 16-18 hours, adding sodium carbonate, stirring at high speed for 15-20 minutes, adding an adhesion and plugging agent, stirring at high speed for 20-30 minutes, adding a water-soluble viscosity modifier, stirring at high speed for 20-30 minutes, adding a polymer performance enhancer, stirring at high speed for 15-20 minutes, adding sodium formate, stirring at high speed for 20-30 minutes, adding a weighting agent, and stirring at high speed for 20-30 minutes, thereby obtaining the high-temperature saline-based drilling fluid suitable for long-term invasion in long horizontal well sections. The medium-speed stirring speed is 1000-2000 r / min, and the high-speed stirring speed is 6000-10000 r / min.

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